https://www.rackspace.com/knowledge_center/article/install-epel-and-additional-repositories-on-centos-and-red-hat
sudo yum install epel-release
#CentOS and Red Hat Enterprise Linux 5.x
wget https://dl.fedoraproject.org/pub/epel/epel-release-latest-5.noarch.rpm
sudo rpm -Uvh epel-release-5*.rpm
#CentOS and Red Hat Enterprise Linux 6.x
wget https://dl.fedoraproject.org/pub/epel/epel-release-latest-6.noarch.rpm
sudo rpm -Uvh epel-release-6*.rpm
#CentOS and Red Hat Enterprise Linux 7.x
wget https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
sudo rpm -Uvh epel-release-7*.rpm